This invention relates to the preparation of donor material for a sutureless corneal transplantation, and more particularly, to a method and apparatus for precisely cutting and preparing the donor material including tabs used for transplanting corneas without the use of sutures.
Corneal transplantation occurs in approximately 37,000 patients in the United States each year. In most conventional transplantations, healing of the recipient's eye is delayed because of the avascular nature of the corneal. The stromal wound healing is facilitated by sutures. However, sutures used in many conventional corneal transplants induce astigmatism. More recently, a sutureless method for corneal transplantation has been developed by Dr. James Rowsey (Rowsey corneal transplant).
FIG. 1 illustrates the Rowsey corneal transplant using the tabbed (sutureless) method. In FIG. 1, a donor material 102 is formed in the shape of a partial sphere having a center portion 103 the size and shape of a central portion of the cornea of an eye. The center portion 103 has a periphery including a downward extending portion 110 and an exterior surface 105 in a convex configuration and an interior surface 107 in a concave configuration with an essentially common thickness throughout. The donor material 102 includes a plurality of corneal tabs 106 extending radially from the periphery of the center portion 103. The top (exterior) surfaces of the tabs 106 are a continuation of the exterior surface 105 of the center portion 103. The exterior surfaces of the center portion 103 (bordered by dotted lines in FIG. 1) and the tabs 106 are of a common Bowman's membrane 108a typically having a thickness of about 100 microns. These tabs typically have a thickness of about 10 percent of the thickness of the center portion 103 of the donor material.
Also illustrated in FIG. 1 is the recipient eye 104. The eye 104 is in the shape of a partial sphere. The recipient eye 104 is formed with a circular aperture 112 at its central portion. The circular aperture 112 is of a size and shape corresponding essentially to the periphery of the center portion 103 and extending portion 110 of the donor material 102. The periphery of the aperture 112 is of a common thickness. The recipient eye 104 also includes a plurality of symmetrically positioned pockets 114. The pockets 114 are incisions made into the thickness of the cornea preferably just under the Bowman's membrane 108b of the recipient eye 104 into the periphery of the aperture 112.
To carry out the transplantation, the central portion 103 of the donor material 102 is positioned within the aperture 112 of the recipient eye 104. The tabbed portions 106 are imbricated into the pockets 114 of the recipient eye 104. Forceps are preferably used for positioning the central portion 103 into the recipient eye 104 and the tabs 106 into their respective pockets 114. Although temporary sutures may also be used to pull the tabs 106 into the pockets 114, in no instance is it necessary to suture the recipient's visual field as is required in conventional transplantation techniques.
Using the above described method, the donor material 102 can be implanted into the recipient eye 104 without the use of sutures in the center portion 103 of the donor material 102. FIG. 2 illustrates a repaired eye with the transplanted cornea. Like reference numerals are used in FIG. 2 to correspond to those elements illustrated in FIG. 1. As can be seen in FIG. 2, the tabbed portions 106 lie within the pockets 114 of the recipient eye 104 and are covered by the Bowman's membrane 108b of the recipient eye 104. The center portion 103 including the downward extending portion 110 of the donor material 102 is placed within the aperture 112 of the recipient eye 104. In this manner, a cornea transplant is carried out in a more simple and straightforward manner without the need for sutures. This method is more fully described in the above-named prior application to which benefit of a filing date is relied upon.
Heretofore, a satisfactory method for preparing the donor material 102 with the necessary precision has not been developed. It is extremely difficult and time consuming to manually prepare a tabbed donor cornea 102 as illustrated in FIG. 1. Moreover, the circle to circle fit from the donor to recipient may leave gaps and/or bulges when manual preparation is used. The radial placement of the donor tabs would be haphazard at best and each implanted cornea would need to be used as the transfer template to prepare the recipient eye. This causes the length of time from the donor to recipient to increase correspondingly and thereby increase the likelihood of damage to the donor material.
Previous efforts to design a tool to carry out the preparation of the donor material 102 have been based on elaborate schemes using plural circular cutting blades combined with linear radial extending blades in order to prepare the tabbed material having the round center portion and the tabbed radially extended portions. Such conventionally suggested tools, however, are unworkable in that the precision required to fashion such a tool is not practical or possible and have not been seriously pursued. Moreover, an extremely important aspect of the sutureless corneal transplant is the ability to prepare the tabbed portions sufficiently thin for insertion into the pockets of the recipient eye. Conventionally suggested designs have not been adequate to accomplish this goal.
A further difficulty encountered by conventional techniques for preparing the donor material, arises from the nature of the donor material to be cut. The donor material exhibits properties very much like innertube tire rubber. The properties of the material make it extremely difficult to cut through the donor material with the precision necessary to prepare the tabbed donor form. Accordingly, a tool used to cut the donor material should also be designed to support the donor material as it is being cut.
It is, therefore, an object of the instant invention to provide a tool which can be used to create replacement cornea including multiple tabs from a donor cornea in a straight forward manner and which is sufficiently precise to properly prepare that the donor material.